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FLO

William Optics RedCat 51 APO

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Posted (edited)

Posted this on another thread, but I might get more visibility here.

Trying to wrap my head around exactly what I would need to adapt both a Canon DSLR and and ZWO ASI178MC. The DSLR is easy as there are EOS T-mounts with M48 threads that give you the exact spacing required. What I can't quite suss out is the ZWO camera. The T2 ring on the ASI178MC, and the ASI178MC itself, has M42 threads. Would I just then need an M48 to M42 adapter? Would I need any spacers since I'm not using a filter wheel? Do I need to remove the T2 ring and attach the camera directly using a female-female adapter? No one has posted any close up pictures of the connections between the scope and such a camera yet or detailed exactly what they used.

It's hard for me to visualize without one in my hand and know exactly what I need to get the correct spacing and I don't want to buy a bunch of extra parts that I don't need and I certainly don't want to wait until I get the scope only to find out everything I do need and have to wait even longer. With the ZWO T2 ring, the camera sensor is 12.5mm back from the face of the T2 ring, the WO M48 to M42 adapter is 7.2mm (Not sure this is correct as it just says this is the thickness, not the spacing). The mechanical drawing of the RedCat says the focal plane is 59.7mm behind the M48 threads. Doing the math, I would still need an additional 40mm (59.7-12.5-7.2=40) of spacing is that correct?


EDIT:
Oh, and the diagonal if I wanted to do a bit of visual. How exactly does that attach and does it require a special diagonal?

Edited by Buzzard75

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The RedCat has Petzval optics so, if you haven't already got one, you need only a M48 to T2 adapter to attach your ZWO camera. 

The RedCat is intended for astrophotography but we hear WO are planning to release a diagonal sometime in April (they say). 

HTH, 

Steve 

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The 59.7mm distance quoted is so that the scope is focused at infinity when the focuser is fully back. I think there is possibly 1mm or a bit less spare so you can actually go through infinity focus. I made the spacing about 59mm so I had a bit more to play with. Using a smaller distance than recommended it will still focus at infinity but the focuser will need extending more. If using it for terrestrial photos this would increase your near focus distance but for astro use this isn't that important.

I believe that to use a diagonal you have to remove the M56 to M48 adaptor to give you more distance to play with though an M56 diagonal is hard to find. I think WO will probably release one for use with this scope.

Alan

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Posted (edited)
3 hours ago, FLO said:

The RedCat has Petzval optics so, if you haven't already got one, you need only a M48 to T2 adapter to attach your ZWO camera. 

The RedCat is intended for astrophotography but we hear WO are planning to release a diagonal sometime in April (they say). 

HTH, 

Steve 

Steve,

Thanks! I had heard that before and have a very basic understanding of why the Petzval design lends itself to photography rather than visual. I'm just thinking for minimalisms sake that a lens/scope that's amazing at photography and so-so at visual work is better than having to take one for each on travel. Especially when it will mostly be used as an AP scope rather than visual.

Wondered if there were any diagonals that had a threaded nosepiece that could be removed with M56 or M48 threads or maybe fitted with an adapter. I assumed there was something out there already. I do see that WO is going to be making one or already has. There is a 1.25" erecting prism on their website, but I don't know if it's the same one they are showing in images of the scope.

Edited by Buzzard75

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9 hours ago, FLO said:

Others have found the same so we recently added this note to our product description page: 

* Some customers have found William Optics' Vixen style dimension a little too narrow for their mount's saddle so you might need to fit a different dovetail. 

HTH, 

Steve 

What I have found is that the jaws on some vixen style clamps are too deep (eg on the Baader clamp) so that the ridge on the top of the redcat bar gets in the way, and cause the bar to ride up a bit.  But other clamps, eg the standard clamp on a skywatcher AZ-eq5 or the ADM dual vixen/losmandy clamp, are a bit shallower and don't have any problem.  The redcat bar is also  about 1.5 - 2mm narrower than another vixen dovetail bar that I have.

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I have one of the redcat's on order but have just seen this video - https://youtu.be/5w5l6gwdjmg and I am curious if there is anyone with an opposing opinion ?

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Posted (edited)

Thanks for the link R3tro. After sitting though the 1 hour video he didn't compare any images of the two lenses, never mind star images, which should be the main point really. Many camera lenses don't produce good star shapes when fully open particularly at the edges. I 'll have to search for sample star images taken with the Canon 300mm. I've tried astro pictures taken with my Canon L 100-400 zoom and the star shapes were awful towards the edges at all zoom positions and unusable really. I know a zoom is worse than a fixed lens in that respect. My Samyang 14mm and Sigma 50mm fixed lenses are also bad on stars all over the field. The only lens I have that gives good star shapes into the corners is the Canon 40mm 'pancake' lens.

The bird image only shows the centre as he says so tells you nothing really except that a Petzval lens is sharp in the centre. I'm not sure how the WO design corrects the inherent field curvature. The Petzval front doublet causes coma. The second doublet corrects the coma (in theory) but introduces field curvature, causing the rapid fall off in focus towards the edges. In the two Redcats (one white) I've tried the flatness looks pretty good, but the coma correction is off. If Es' Reid can fix that I'd be happy with the Redcat. :smile:

I'd agree that the RedCat is really no good for wildlife photography as the focuser is far to stiff  for quick adjustment and needs two hands on the focuser to make small adjustments. Pre-focusing on a certain position and hoping the subject appears in the right spot is the only way. The focus tension ring isn't needed really as the no tension stiffness would prevent the lens moving by itself anyway. One handed focusing always causes it to overshoot if you try to nudge it, as you need to apply so much force that a second hand to 'brake' the focuser is required (when using the bahtinov mask for fine focus).

Alan

Edited by symmetal

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I now have the RedCat and the Canon 300 f/4 so will take some comparison astro' images when skies allow.

Dave

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8 hours ago, symmetal said:

Thanks for the link R3tro. After sitting though the 1 hour video he didn't compare any images of the two lenses, never mind star images, which should be the main point really. Many camera lenses don't produce good star shapes when fully open particularly at the edges. I 'll have to search for sample star images taken with the Canon 300mm. I've tried astro pictures taken with my Canon L 100-400 zoom and the star shapes were awful towards the edges at all zoom positions and unusable really. I know a zoom is worse than a fixed lens in that respect. My Samyang 14mm and Sigma 50mm fixed lenses are also bad on stars all over the field. The only lens I have that gives good star shapes into the corners is the Canon 40mm 'pancake' lens.

The bird image only shows the centre as he says so tells you nothing really except that a Petzval lens is sharp in the centre. I'm not sure how the WO design corrects the inherent field curvature. The Petzval front doublet causes coma. The second doublet corrects the coma (in theory) but introduces field curvature, causing the rapid fall off in focus towards the edges. In the two Redcats (one white) I've tried the flatness looks pretty good, but the coma correction is off. If Es' Reid can fix that I'd be happy with the Redcat. :smile:

I'd agree that the RedCat is really no good for wildlife photography as the focuser is far to stiff  for quick adjustment and needs two hands on the focuser to make small adjustments. Pre-focusing on a certain position and hoping the subject appears in the right spot is the only way. The focus tension ring isn't needed really as the no tension stiffness would prevent the lens moving by itself anyway. One handed focusing always causes it to overshoot if you try to nudge it, as you need to apply so much force that a second hand to 'brake' the focuser is required (when using the bahtinov mask for fine focus).

Alan

Thank you for the comment Alan, I am currently using a Sony A7R3 and a 100 to 400 G-Master and samyang 14mm for astro and while the 100 to 400 is a sharp lens for wildlife and also great for motionless wildlife manually, I find for astro it is very hard to focus due to the "focus by wire" nature which is why I decided to purchase the Redcat (not yet available, which has given me time to pause).

Indecently, I have also pointed William Yang to the video because there is a general negative vibe towards the Redcat.

What would you suggest scope wise, would you stick with the cat or go for something different? 

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8 hours ago, Davey-T said:

I now have the RedCat and the Canon 300 f/4 so will take some comparison astro' images when skies allow.

Dave

That would be great thank you Dave!

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Hi, I have a reply from William Yang and would like to post on here (quite reassuring) but the text appears black so doesn't show with black background, any way to change this ? It is quite a long mess age.

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6 minutes ago, R3tr0 said:

Hi, I have a reply from William Yang and would like to post on here (quite reassuring) but the text appears black so doesn't show with black background, any way to change this ? It is quite a long mess age.

After you've pasted it try highlighting it and changing the text colour to white, forth button from the right above.

Dave

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paste the text into notepad then recopy as that strips any formatting

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18 minutes ago, R3tr0 said:

Hi, I have a reply from William Yang and would like to post on here (quite reassuring) but the text appears black so doesn't show with black background, any way to change this ? It is quite a long mess age.

If you post it and it doesn’t show correctly we can remedy that ?

We are assuming William Yang is happy for you to post his email to you on a public forum... 

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15 minutes ago, Steve said:

If you post it and it doesn’t show correctly we can remedy that ?

We are assuming William Yang is happy for you to post his email to you on a public forum... 

Good point, I will check with him.

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Hi 

While I did have further conversations with William Yang, I did not receive permission to post any of the emails he sent me, this is understandable considering we were discussing the video I linked from you tube. 

He is very passionate concerning this scope and I don't think he will mind me quoting that "I consider the Redcat 51 our best product from the past 22 years since WO established in 1996.". So I think he has more than a little confidence in the Redcat. 

I look forward to recieving this scope!

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These images were take just last week with the Redcat, supplied via William Yang.

Stunning!

IMG_3707.JPG

IMG_3694.jpg

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I knew this little scope would be an AP gem, not for any reason other than it looks awesome lol.

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1 hour ago, R3tr0 said:

These images were take just last week with the Redcat, supplied via William Yang.

At least it shows that a properly aligned RedCat can produce very good results which is encouraging. Was this an off the shelf scope or one that was given a more rigorous alignment session for promotional purposes. Was the sensor size mentioned, and was the image cropped? ?

Alan

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9 hours ago, symmetal said:

At least it shows that a properly aligned RedCat can produce very good results which is encouraging. Was this an off the shelf scope or one that was given a more rigorous alignment session for promotional purposes. Was the sensor size mentioned, and was the image cropped? ?

Alan

He did not say, he just thought I would like them. I would assume there is some cropping going on but don't know. I have asked for setup details used on the images .

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Ok, William got back to me with some info on this image - 

No filters , Total exposure time 4.5 hours,  Using Nikon D800 mod, 5 minutes each shot and stacked  All together processing by Pixinsight and photoshop .

IMG_3694.jpg

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Holy moly, great looking shots. If I already have a nikkor 180mm f2.8, is there a reason to jump on this purchase? Or should I go longer to image smaller objects? I use a star adventurer and nikon d7100 btw.

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5 hours ago, bokchoy ninja said:

Holy moly, great looking shots. If I already have a nikkor 180mm f2.8, is there a reason to jump on this purchase? Or should I go longer to image smaller objects? I use a star adventurer and nikon d7100 btw.

Not necessarily, you should be able to get great images from your set up, I also use the star adventurer and properly aligned should get 5+ minute exposures, alot relys on stacking software and skills with Photoshop/lightroom and this was using an astro modded D800.

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On 14/04/2019 at 21:50, R3tr0 said:

While I did have further conversations with William Yang, I did not receive permission to post any of the emails he sent me, this is understandable considering we were discussing the video I linked from you tube.

To me, that is suspicious

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